Ink jet printing is accomplished by ejecting ink from a nozzle toward paper or another print medium. The ink is driven from the nozzle toward the medium in a variety of ways. For example, in electrostatic printing the ink is driven by an electrostatic field. Another ink jet printing procedure, known as squeeze tube, employs a piezo-electric element in the ink nozzle. Electrically caused distortions of the piezo-electric element pump the ink through the nozzle and toward the print medium. In still another ink jet printing procedure known as thermo or bubble ink jet printing, the ink is driven from the nozzle toward the print medium by the formation of an expanding vapor phase bubble in the nozzle. These various printing methods are described in "Output Hard Copy Devices," edited by Durbeck and Sherr, Academic Press, 1988 (see particularly chapter 13, entitled "Ink Jet Printing").
The ink to be printed by any of the ink jet printing methods is typically stored in an ink chamber. The ink then flows from the chamber to the nozzle where it is ejected toward the print medium. An ink jet printhead can have more than one chamber. For a colored printhead it is preferable that the ink jet printhead have at least two ink chambers. As the number of chambers increases, the overall size of the printhead cartridge must increase or else the volume of each individual chamber must be decreased. Typically, overall printhead size is limited by space constraints in the printer. In addition, it is not desirable to reduce ink volume because this requires replacement of the printhead cartridge more frequently.
The prior art, such as U.S. Pat. No. 4,812,859, Chan, et al., issued Mar. 14, 1989, teaches the use of multi-chamber ink jet printheads wherein the individual ink chambers are aligned side-by-side. When the printhead contains three or more ink chambers and the chambers are aligned linearly, the ink from the chamber farthest from the nozzle must flow across at least one chamber width before arriving at the nozzle. This wastes ink as the entire length of the flow channel must be filled with ink. In addition, the side-by-side arrangement of all of the chambers provides a very wide and cumbersome printhead.
U.S. Pat. No. 4,513,296, Okamura, issued Apr. 23, 1985, teaches the use of L-shaped chambers stacked one inside the other in a side-by-side arrangement. Several individual nozzles, one for each ink chamber, are arrayed in a linear fashion across the face of the printhead. Because of the use of multiple nozzles, rather than one centralized nozzle, this configuration requires a relatively large space within the printer.
Accordingly it is clear that a need exists for an ink jet printhead that reduces the overall width of the printhead cartridge without reducing either the individual volumes defined by each ink chamber or the total combined volume of all of the ink chambers.